People who seem to face stressful situations without blinking an eye may have an increased risk of health woes such as obesity and depression, according to a new study.

These results mean that when the body underreacts to stresses in life, it can be just as bad for your health as overreacting, said study researcher Doug Carroll, a professor in the School of Sport and Exercise Science at the University of Birmingham in England.

Over-responding to stressors can increase the risk of hypertension and atherosclerosis, but under-responding to stressors may be associated with obesity, depression, poor immune functioning and poor overall health, Carroll said.

The finding doesn't necessarily apply to all people with relaxed personalities, Carroll said. "It's important to distinguish between two things: First, the outward appearance of 'being chilled' and what your biology is actually doing, [and] second, between the resting biological state and how that biology reacts to stress," Carroll told MyHealthNewsDaily.

"Obese individuals tend to have high resting heart rates, but low or blunted heart-rate reactions to stress," he said.

Researchers analyzed health data collected from 1,300 people during a 14-year period.

When participants were asked to complete a short stress test, those who did not have large heart rate or blood pressure changes were more likely to become depressed and obese over the next five years, compared with those whose heart rates and blood pressures increased in response to stress, the study said.

The people whose heart rates weren't affected by the stress test were also more likely to say they were in poor health than people whose heart rate and blood pressure increased during the test, according to the study.

Past research has linked low blood pressure with depression. A 2000 study of more than a thousand people in the British Journal of Psychiatry found that low blood pressure was a risk factor for, and not a consequence of, depression.

And a 2006 study in the Journal of Epidemiology & Community Health found that people with low blood pressure are more likely to suffer from anxiety and depression than people with normal blood pressure levels.

Carroll and his colleagues are now looking at the effects of a blunted reaction to stress in other studies. Next, they hope to look at the relationship between cognitive ability (reasoning and speed of reaction) and reactions to stress , because people who have high reactions to stress may have better cognitive abilities than those who have low reactions, he said.

The study was published online Dec. 15 in the journal Biological Psychology.

Pass it on: People who have low reactions to stress have an increased risk of depression and obesity.

Amanda Chan

Amanda Chan was a staff writer for Live Science Health. She holds a bachelor's degree in journalism and mass communication from the Walter Cronkite School of Journalism and Mass Communication at Arizona State University, and a master's degree in journalism from Columbia University.